Pneumatic safety edge for power operated doors



July 12, 1966 N. K. MILLER 3,260,312

PNEUMATIC SAFETY EDGE FOR POWER OPERATED DOORS Filed Jan. 51, 1964 INVENTOR. NORM/UV M/LLEE United States Patent 3,260,812 PNEUMATIC SAFETY EDGE FOR POWER OPERATED DOORS Norman K. Miller, Havertown, Pa., assignor to Miller Brothers, Upper Darby, Pa., a partnership Filed Jan. 31, 1964, Ser. No. 341,639 1 Claim. (Cl. ZOO-61.43)

The present invention relates to a safety edge of a power operated door and is concerned primarily with the elimination of electric contacts within the edge itself.

As the name implies a power operated door is ordinarily moved by an electric motor. It has long been recognized as desirable that the motor to be de-energized when the door encounters some object or person in its movement. Thus, the doors have been provided with safety edges. In the past these edges have included electric contacts which when brought into engagement by the door striking an object disables the motor.

In many places where power doors are installed the liability of an explosion is a serious factor. A good example would be in a factory which produces explosives. In such locations the possibility of the electric contacts in the safety edge creating a spark which would ignite an explosion is a serious danger.

With this condition in mind, the present invention has in view as its foremost objective, the provision of a safety edge for a power operated door in which all electric contacts are avoided and the impulse for disabling the motor is genera-ted by a pneumatic system.

In accordance with the present invention the electric motor which powers the door is located in a safety zone removed from the explosive hazard. Included in the circuit of the motor is a pneumatic-ally operated switch with a piece of tubing extending from the switch to the pneumatic system on the door edge.

It is of course important that the power operated movement of the door be discontinued immediately an object is encountered. Thus, the pneumatic device of the door edge and conducting tubing must be so related that any increase in pressure within the door edge will be translated into an impulse which will operate the switch.

With this thought in mind a further object of the invention is to provide a safety edge of the character aforesaid of comparatively large crosssectional area with the conducting tube that connects the edge with the switch being of relatively small cross-sectional area. The large edge is easily deformed upon impact with an object and its volumetric content diminished to increase the air pressure therewithin. This results in an impulse which is conducted by the tube to the motor switch.

A further object of the invention is to provide a safety edge of the type noted which consists essentially of an air impervious casing which is held in a generally square or rectangular shape by an inner wall structure of foam rubber. This wall structure in turn defines a central passage or recess. The foam rubber is formed with perforations of various sizes and spacings and the sensitivity of the edge is determined by the size and number of these perforations.

Various other more detailed objects and advantages of the invention such as arises in connection with carrying out the above noted ideas in a practical embodiment will in part become apparent and in part be hereinafter stated as the description of the invention proceeds.

The invention therefore comprises a pneumatic safety edge for power operated doors which consists essentially of an air impervious fabric casing enclosing a wall structure of perforated foam rubber with the casing being 3,260,812 Patented July 12, 1966 connected to a motor control switch by a tube of relatively small diameter.

For a full and more complete understanding of the invention reference may be had to the following description and accompanying drawing, wherein:

FIGURE 1 isa diagrammatic view of a power operating door with the safety edge of this invention applied thereto.

FIGURE 2 is a horizontal section through the safety edge and a portion of the door.

FIGURE 3 is a view taken normal to the showing of FIGURE 2 and is partly in section and partly in elevation, and

FIGURE 4 is a detailed prospective illustrating the tube connection.

Referring now to the drawing and first more particularly to FIGURE 1, the wall of a building such as an explosive factory is indicated at 10. Operatively mounted in the wall 10 is a door 11. The door 11 is moved by a motor represented diagrammatically at 12 in FIGURE 3. A control switch 13 is included in the circuit of the motor 12 and in the embodiment of the invention illustrated when the switch 13 is closed, the motor 12 is disabled.

At this point, it might be well to note that the door 11 is hown as being of the hinged type. The invention is equally susceptible when used on a sliding or collapsible type door.

Mounted on the free edge of the door 11 is a safety edge which is referred to in its entirety by the reference character S. The edge S comprises two walls 14 and 15 in the form of strips of foam rubber and which are maintained, separated, or in spaced relation by narrow strips 16 and 17 also of foam rubber. The strips 14, 15, 16, and 17 define a general square shape which provides a central passage or recess 18. All of the strips 14, 15, 16, and 17 are also formed with perforations 19; the number and size of which determine the sensitivity of the edge. The strips 14, 15, 16, and 17 are enclosed by an air impervious lining 20 which may be vinyl or any suitable plastic and the lining enclosed by a fabric casing 21. The lining 20 and fabric 21 are continued out at one side to provide an attaching flap 22 that is used in mounting the edge S on the door 11.

Communicating with the interior of the edge S is a nipple 23 having a bore 24 of relatively small diameter. This nipple is located at any convenient point on the edge S. A tube 25, preferably flexible, extends from the nipple 23 to the switch 13.

Operation It will be understood that the interior of the edge S has a comparatively large volumetric content. Thus, it will enclose a large mass of air. The ease with which the wall structure may be deformed is determined by the number and size of the perforations 19. Thus, for increased sensitivity a large number of large size perforations are included. If the edge is to be more rigid and resistant to deformation the number and size of the openings is reduced.

FIGURE .3 illustrates what happens when the edge S encounters an object in its path of movement. The impact is represented at 26 and this impact results in a decrease in the volumetric content of the edge. This in turn results in an increase in air pressure which is translated into an impulse which emits from the nipple 23 and transmitted through the tube 25 to the switch 13, the latter is closed and the door disabled.

While preferred specific embodiments of the invention are hereinbefore set forth, it is to be. clearly understood that the invention is not to be limited to the exact construction, materials, and devices illustrated and described ecause various modifications of these details may be provided in putting the information into practice within the purview of the appended claim.

What is claimed is:

The combination of an electric motor operated door with a switch controlling the operation of the motor, and a safety edge for said door, said safety edge comprising an elongated wall structure of perforated foam rubber with the wall structure defining a central recess, an airimpervious vinyl lining enclosing said Wall structure, a fabric casing about said lining, said lining and casing including a tab which attaches said safety edge to the door, a nipple carried by said casing and communicating with said recess, and a flexible tube operatively connecting said nipple to said switch, said nipple and tube having 4 a :bore of a cross-section smaller than the cross-section of said recess.

References Cited by the Examiner UNITED STATES PATENTS 2,783,325 2/1957 Luckey 200-86 X 2,795,668 6/1957 Puckett 20086 X 2,843,690 7/1958 Miller 20061.43

FOREIGN PATENTS 342,157 1/1931 Great Britain.

BERNARD A. GILHEANY, Primary Examiner.

I. I. BAKER, Assistant Examiner. 

